Hyperloop—a theoretical 760 mph transit system made of sun, air, and magnets

Musk's elaborate plan for a futuristic transit system is now open-source.

Concept sketches of the Hyperloop passenger capsules; note the air intake noses.

Tesla Motors

The proposed design for the “Hyperloop,” an ultra-fast transit system that would run between San Francisco and Los Angeles, was revealed today in a 56-page PDF document on Elon Musk’s Tesla Motors website. Musk, the founder of SpaceX and Tesla Motors, describes a system that moves pods under low pressure through a tube between the two cities following the I-5 freeway.

The Hyperloop would consist of aluminum pods inside a set of two steel tubes, one for each direction of travel and connected at each terminus. The tubes would be positioned on top of pylons spaced 100 feet apart holding the tube 20 feet in the air, and the tube would be covered by solar arrays to generate its own power.

Inside the tubes, the pods would carry people at speeds of up to 760 miles per hour. The pods would each carry 28 passengers and depart every two minutes from either location (or every 30 seconds at peak times). So each pod would have about 23 miles between one another while traversing the tube. The transport capacity would therefore be about 840 passengers per hour.

A translucent view of the parallel tubes, mounted on their pylons.

Tesla Motors

The capsules’ speed would rely in large part on a low-pressure environment, about “1/6 that of the pressure of the atmosphere on Mars” or a fraction of a percent of that on Earth, maintained by vacuum pumps. This would reduce drag by 1,000 times, the document says.

The tubes would not use a “hard vacuum” because they are “expensive and difficult to maintain compared with low pressure solutions.” A pneumatic tube is fine for your bank, but it does not make an attainable, sophisticated transport solution.

The passenger capsules would be 4.43 feet at their widest point and 6.11 feet at their tallest. They would each weigh about 7,700 pounds and cost $275,000 to make ($1.35 million including all the onboard equipment, mechanical parts, and support systems). Musk envisions the passengers sitting in reclined chairs in rows of two with their feet elevated, as if relaxing in a chaise longue.

Each of the pods would have 28 attached “air bearing” skis that would “[float] on a pressurized cushion of air” a fraction of an inch away from the surface of the tube. The skis would be lifted off the surface by injecting air into the gap, a method that the document says is effective either when the capsules are stationary or moving very fast.

The tubes would have either gull-wing or sliding doors, the document says. We don't know what optimistic version of humanity they're working with, but we've never met a group of 28 people who can load up a cabin in 20 minutes, let alone two minutes.

Tesla Motors

Inlets on the two noses of the capsules would serve as air intake sources, reducing the “choking flow” of air around the capsule as it moves through the tube. Removing air in the tube would not only smooth the capsule’s journey, it would feed the skis that the capsule needs to skate along on.

The air from the inlets would be processed by a compressor and then stored in a reservoir onboard the capsule. The capsule would then eject this air through grooves on the bottom of the skis, generating enough lift to support it that fraction of an inch away from the surface.

As for actually moving the capsules, acceleration in an environment like this is a huge concern. While human beings don’t care that much about being transported at supersonic speeds in enclosed environments, how they arrive at those speeds can be a huge problem. Generally, more than an extra g of force is extremely uncomfortable. So the design here takes care not to accelerate people too quickly.

The Hyperloop's capsules would be propelled by linear induction motors spaced throughout the tube. Magnets on the tube’s internal surface would function as the stator, with an electric current supplied to them to generate a magnetic field. Magnets on the capsule would function as the rotor, spurred on by those in the tube. Those accelerators would also have two inverters that would push outgoing capsules along while capturing energy from incoming capsules that are slowing down (while there is one tube for each direction of travel, this means the directions for either could be reversed).

The capsules would travel at a “relatively low speed” between 0 and 300 miles per hour while entering and exiting urban areas and maintain at about 300 mph while crossing mountainous areas. Once they reach the flatter I-5 stretch, they could be sped up by the linear accelerators to up to 760 mph to coast at roughly that speed for the bulk of the journey.

A rough graph of transit velocities at various points along the Hyperloop journey.

Tesla Motors

The document points out that a Hyperloop tube covered in solar arrays could generate about 52MW of power, a vast amount more than the estimated 6MW that would be needed to operate the Hyperloop itself.

Musk addresses some of the disaster scenarios that the Hyperloop tube might encounter. Since the Hyperloop capsules spend the most time coasting, the proposal states that they don’t need much power to travel, but everything needing power would be supplemented by lithium ion batteries. If a capsule depressurized, the control system would use the onboard pressurized air to maintain the environment until the capsule reached its destination. Worst case, oxygen masks would drop for the passengers.

The proposal states that it would be hard for a capsule to become stranded within the tube given that it spends most of its time coasting at a high speed (“no propulsion required for more than 90 percent of the journey). If a capsule was truly rendered immobile by its normal means of travel, however, it would use “small onboard electric motors” to power “deployed wheels” so the cabin could roll itself to safety.

It’s difficult not to imagine a partial loss of sanity among passengers who, thinking they’re in for a half-hour journey, suddenly find themselves taking 10 times as long to get there. Hopefully it wouldn’t be a frequent occurrence. The document makes special note that all capsules would be supplied with enough air to support the passengers even for this failure scenario of a suddenly-normal-length trip.

The alpha proposal still pegs the cost at $6 billion: $54 million to construct the 40 passenger capsules and $5.41 billion for the tube and propulsion system construction.

Even more ambitiously, the Hyperloop document suggests that not only people could benefit from a transportation upgrade. A “cargo capsule” system that could also transport vehicles would cost another $30.5 million for 20 capsules, plus another $1.5 billion for a more robust tube system—a total of $7.5 billion. But in this kind of futuristic world, who’s going to need cars anymore?

Promoted Comments

Any idea how the cars will enter vacuum? I assume the station has to be in air. If it goes through an airlock, that means pumping down a volume the size of a city bus in about a minute (or less than 30 seconds during rush hour). That's a hell of a pump.

They could do it with differential pumping; staged pumps with steadily increasing vacuum (lowering pressure) the farther you get from the station. Since the thing isn't moving very fast for the first half kilometer or so, drag isn't a big deal and hence there's plenty of space to maintain a reasonable pressure gradient from atmosphere down to whatever the operating pressure is for the bulk of the line.

I do not see why this thing should be significantly cheaper than a maglev train a in comparison much advanced technology which didn't have enough advantages against a normal train as well and which ended up much more costly than initially thought.

He addresses the maglev point briefly in the introduction. Basically magnets are expensive. Lining several hundred miles of track with high-strength magnets would cost a fortune. Air suspension is a more scalable solution.

Now that I think about it, if you are in a tube, you have to have air capture and compression system anyway, to prevent building up a compression wave ahead of the train. Might as well re-use this air in some useful fashion.

Magnets on the tube’s internal surface would function as the stator, with an electric current supplied to them to generate a magnetic field. Magnets on the capsule would function as the stator, spurred on by those in the tube.

Which is the stator? Presumably the car has permanent magnets and there are electromagnets in the tube body.

Pumping out a few hundred miles worth of tubing, even to a low vacuum, is not trivial to put it mildly.

Magnets on the tube’s internal surface would function as the stator, with an electric current supplied to them to generate a magnetic field. Magnets on the capsule would function as the stator, spurred on by those in the tube.

Which is the stator? Presumably the car has permanent magnets and there are electromagnets in the tube body.

Pumping out a few hundred miles worth of tubing, even to a low vacuum, is not trivial to put it mildly.

Whoops, that's my error. The tube acts as the stator, per the document.

840 people per hour. Not too shabby. An ice takes 400. Sure you could run more than two per hour but that rarely happens.

But in the end the advantages over a decent traditional high speed rail link (200mph speed similar capacity very low energy usage) seem to be somehow low. And you get lot of new question marks. It might just be that California sucks at building infrastructure (I have seen your highways) and a completely new model doesn't help much with that.

I do not see why this thing should be significantly cheaper than a maglev train a in comparison much advanced technology which didn't have enough advantages against a normal train as well and which ended up much more costly than initially thought.

Any idea how the cars will enter vacuum? I assume the station has to be in air. If it goes through an airlock, that means pumping down a volume the size of a city bus in about a minute (or less than 30 seconds during rush hour). That's a hell of a pump.

Any idea how the cars will enter vacuum? I assume the station has to be in air. If it goes through an airlock, that means pumping down a volume the size of a city bus in about a minute (or less than 30 seconds during rush hour). That's a hell of a pump.

This is speculation, but I imagine once the capsules entered an airlock, the intake noses and compressor could do some of the work pulling air out of the space, "fueling" themselves up for the journey.

Any idea how the cars will enter vacuum? I assume the station has to be in air. If it goes through an airlock, that means pumping down a volume the size of a city bus in about a minute (or less than 30 seconds during rush hour). That's a hell of a pump.

They could do it with differential pumping; staged pumps with steadily increasing vacuum (lowering pressure) the farther you get from the station. Since the thing isn't moving very fast for the first half kilometer or so, drag isn't a big deal and hence there's plenty of space to maintain a reasonable pressure gradient from atmosphere down to whatever the operating pressure is for the bulk of the line.

I do not see why this thing should be significantly cheaper than a maglev train a in comparison much advanced technology which didn't have enough advantages against a normal train as well and which ended up much more costly than initially thought.

He addresses the maglev point briefly in the introduction. Basically magnets are expensive. Lining several hundred miles of track with high-strength magnets would cost a fortune. Air suspension is a more scalable solution.

Now that I think about it, if you are in a tube, you have to have air capture and compression system anyway, to prevent building up a compression wave ahead of the train. Might as well re-use this air in some useful fashion.

Magnets on the tube’s internal surface would function as the stator, with an electric current supplied to them to generate a magnetic field. Magnets on the capsule would function as the stator, spurred on by those in the tube.

Which is the stator? Presumably the car has permanent magnets and there are electromagnets in the tube body.

Pumping out a few hundred miles worth of tubing, even to a low vacuum, is not trivial to put it mildly.

Magnets on the tube’s internal surface would function as the stator, with an electric current supplied to them to generate a magnetic field. Magnets on the capsule would function as the stator, spurred on by those in the tube.

Which is the stator? Presumably the car has permanent magnets and there are electromagnets in the tube body.

Pumping out a few hundred miles worth of tubing, even to a low vacuum, is not trivial to put it mildly.

It's not a vacuum. Each capsule draws the air from in front of it with a turbine.

EDIT: Dang, hasn't anyone read it? It's not a vacuum, guys.

I'm not saying it's totally practical, but it's definitely more realistic than a giant airless tube.

They quote a number which is "1/6 of the atmosphere of Mars'. Martian atmospheric pressure is something like 600 pascals, compared to 100 kilopascals for Earth. 1/6 of 600 is 100 Pa, or 0.1% of Earth's atmospheric pressure. 1 mbar is a rough vacuum, but it's a vacuum.

Nice idea, BUT. I can't imagine a better target for terrorists. Can you imagine what would happen if the tube was ruptured in the middle somewhere, with tons of these things in-flight towards the rupture? I don't want to think about it. Nor do I want to think about how claustrophobic that thing would be. Like being trapped in a supersonic coffin.

I do not see why this thing should be significantly cheaper than a maglev train a in comparison much advanced technology which didn't have enough advantages against a normal train as well and which ended up much more costly than initially thought.

He addresses the maglev point briefly in the introduction. Basically magnets are expensive. Lining several hundred miles of track with high-strength magnets would cost a fortune. Air suspension is a more scalable solution.

Now that I think about it, if you are in a tube, you have to have air capture and compression system anyway, to prevent building up a compression wave ahead of the train. Might as well re-use this air in some useful fashion.

Maglev also isn't really happening despite consuming billions of dollars for decades. OK, so there is one 20 mile line operating in China and the Japanese will probably eventually have maglev Shinkansen but it seems clear that one does not simply build a maglev rail system.

I'm not saying some completely new proposal that has never even been prototyped is an obviously better idea, just pointing out that maglev appears to be a very difficult technology to implement and put into service in a meaningful way.

Magnets on the tube’s internal surface would function as the stator, with an electric current supplied to them to generate a magnetic field. Magnets on the capsule would function as the stator, spurred on by those in the tube.

Which is the stator? Presumably the car has permanent magnets and there are electromagnets in the tube body.

Pumping out a few hundred miles worth of tubing, even to a low vacuum, is not trivial to put it mildly.

It's not a vacuum. Each capsule draws the air from in front of it with a turbine.

EDIT: Dang, hasn't anyone read it? It's not a vacuum, guys.

I'm not saying it's totally practical, but it's definitely more realistic than a giant airless tube.

They quote a number which is "1/6 of the atmosphere of Mars'. Martian atmospheric pressure is something like 600 pascals, compared to 100 kilopascals for Earth. 1/6 of 600 is 100 Pa, or 0.1% of Earth's atmospheric pressure. 1 mbar is a rough vacuum, but it's a vacuum.

Yeah, I agree. I had skimmed the original PDF before dropping in here.

It's NOT a vacuum. However, it is low-enough pressure to seem fairly outlandish.

At 840 persons per hour, assuming maximum utilization the capital cost alone of this thing is going to be on the order of $110 per person (for 30 year financing at 8%) - assuming 100% utilization. That's a little unreasonable (because most people travel during the day, and it's also not possible) so the true cost is something more like $250.

A plane ticket between LAX and SFO costs about $150, retail. Flight time is about an hour and ten minutes, so you're saving somewhere between 40 minutes and 160 minutes (depending on how you count the airport time), at a cost of about $100. This doesn't account at all for things like downtime (which loses revenue), or, you know, paying for anything but the physical tube + riders.

High marks for the 'neat idea' part, low marks for practicality. Needs to be a lot bigger. How did he come up with those diameters, anyways? You need to put a lot more people on a car to make it up.

And another thing: how are you going to setup the station to launch cars every thirty seconds? That's going to be an enormously complex switching system.

Yeah. Bigger cars. That'd fix it. Or "trained" cars that are linked.

Also, what happens if there is a break in the line? Not from a pressure perspective, but from a 'cars-falling-to-the-ground' perspective?

Any idea how the cars will enter vacuum? I assume the station has to be in air. If it goes through an airlock, that means pumping down a volume the size of a city bus in about a minute (or less than 30 seconds during rush hour). That's a hell of a pump.

This is speculation, but I imagine once the capsules entered an airlock, the intake noses and compressor could do some of the work pulling air out of the space, "fueling" themselves up for the journey.

I think a simpler solution would be to have the terminal and car come into near contact for un/loading and then have the terminal extend an airtight gasket to the car just outside the door area. This way you'd only need to pump down an volume equal to the area of the doors multiplied by an inch or twos thickness while leaving the tube itself permanently depressurized. The section of the tube the car itself is sitting in during the un/loading process should still have a separate airtight door closing it off from the rest of the tube, not as the primary vacuum containment system, but as a failsafe.

Nice idea, BUT. I can't imagine a better target for terrorists. Can you imagine what would happen if the tube was ruptured in the middle somewhere, with tons of these things in-flight towards the rupture? I don't want to think about it. Nor do I want to think about how claustrophobic that thing would be. Like being trapped in a supersonic coffin.

We should never allow our advancements to be hindered because some asshole might theoretically strap a bomb to their chest.

Nice idea, BUT. I can't imagine a better target for terrorists. Can you imagine what would happen if the tube was ruptured in the middle somewhere, with tons of these things in-flight towards the rupture? I don't want to think about it. Nor do I want to think about how claustrophobic that thing would be. Like being trapped in a supersonic coffin.

We should never allow our advancements to be hindered because some asshole might theoretically strap a bomb to their chest.

This is exactly why we stopped building airplanes and skyscrapers after 9/11.

I do not see why this thing should be significantly cheaper than a maglev train a in comparison much advanced technology which didn't have enough advantages against a normal train as well and which ended up much more costly than initially thought.

He addresses the maglev point briefly in the introduction. Basically magnets are expensive. Lining several hundred miles of track with high-strength magnets would cost a fortune. Air suspension is a more scalable solution.

Now that I think about it, if you are in a tube, you have to have air capture and compression system anyway, to prevent building up a compression wave ahead of the train. Might as well re-use this air in some useful fashion.

Maglev also isn't really happening despite consuming billions of dollars for decades. OK, so there is one 20 mile line operating in China and the Japanese will probably eventually have maglev Shinkansen but it seems clear that one does not simply build a maglev rail system.

I'm not saying some completely new proposal that has never even been prototyped is an obviously better idea, just pointing out that maglev appears to be a very difficult technology to implement and put into service in a meaningful way.

Exactly that's the point. We have a lot of tech proposals with potential

I'm still stuck on the low pressure requirement. Avoiding calling that vacuum is disingenuous. The power required to pump that much volume down to that low pressure feels like an issue. Maybe I'm wrong.

My concerns about bailing out of the system are still a big deal. You're only a half-hour away from help if they can use the tube. When the system emergency-stops you're in the middle of fly-over land and we may need a way of breaking out of the capsule and (low pressure!) tube.

It’s difficult not to imagine a partial loss of sanity among passengers who, thinking they’re in for a half-hour journey, suddenly find themselves taking 10 times as long to get there. Hopefully it wouldn’t be a frequent occurrence. The document makes special note that all capsules would be supplied with enough air to support the passengers even for this failure scenario of a suddenly-normal-length trip.

This would be a nightmare for all the pods behind the failing unit. Much better to have escape/maintenance junctions to bring the pod(s) out of circulation, I would think.

Great idea for the distant future, but it wouldnt be cheaper than the California High Speed Rail. The higher speeds would require straighter routes, with HIGHER land acquisition and engineering costs.

Or does he think engineering costs for a completely untried technology are cheaper than those for one thats been around for 200 years?

It IS cheaper though, and there's no sort of exotic technology in here, nothing that hasn't been done on a theme park ride before.

They account for land acquisition in the document, there is $1 billion in permits and land costs, but for the most part it's able to follow the existing highway right-of-way. Turns are banked like on an airplane, so that helps significantly.

Nice idea, BUT. I can't imagine a better target for terrorists. Can you imagine what would happen if the tube was ruptured in the middle somewhere, with tons of these things in-flight towards the rupture? I don't want to think about it. Nor do I want to think about how claustrophobic that thing would be. Like being trapped in a supersonic coffin.

Have you ever flown in an airplane before?

From the pics, it looks pretty comfy. Any thoughts on how they can improve it?

Can you imagine what would happen if the tube was ruptured in the middle somewhere, with tons of these things in-flight towards the rupture?

I'm assuming some sort of on-board breaking system gets deployed. It wouldn't be terribly difficult to have brake pads stick out and slam into the tube if a catastrophic failure is registered.

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The higher speeds would require straighter routes, with HIGHER land acquisition and engineering costs.

Which is why he suggested that it could hug the I-5 route. Land already acquired, and the system could be put next to it.

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Flight time is about an hour and ten minutes, so you're saving somewhere between 40 minutes and 160 minutes (depending on how you count the airport time)

Having scheduled a LOT of business travel, I can easily say that you pretty much have to add in at least an hour of time at the airport when arriving, and at least 45 minutes after landing for general airport related stuff like check-in, security checks, and loading and unloading from the plane. That's just if you're traveling with a carry-on. For distances like Seattle to Portland, it's literally faster and easier to just drive than to fly. I'm not saying that this system would be a walk up, get in, and depart sort of deal. But it would still likely to be a substantially less time consuming process.

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Nor do I want to think about how claustrophobic that thing would be. Like being trapped in a supersonic coffin

This would probably be a non-starter for someone like my wife, who does have claustrophobia. Small enclosed tube? Yeah, she'd have a panic attack just looking at the concept drawings.

First, cars would only run with passengers. With a low per-car volume, it's not difficult to fill them for the trip. If it's an as-needed basis, then you don't have to worry so much about slow times except in cases where the cars end up piling up on one end of the loop.

Plus, one of the things that is almost universally unregarded is the time saved for those making the journey. For those who would most make use of such a system, it could translate into increased productivity to the tune of millions not wasted in transit.